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Monday, July 09, 2007

Informed debate needed on climate change not poor use of science

Two recent letter writers make basic scientific mistakes in their statements about climate change in the local press. People contributing to public debate on the issue should take great care to get all the facts about this complex matter straight. There is a danger that the public could be misled into thinking that there is not a big problem when there is, and that there is no need to take action, changing our behaviour, when there is an urgent need.

Pearl V Smith feels the expansion of Bristol Airport is fine because 'The airport is surrounded by trees, and they absorb carbon and give off oxygen - many, many more trees than Bristol has.' ('Trees near airport suck up pollution', Bristol Evening Post letters, July 6). First: there are nowhere near enough trees to absorb all the carbon. Second: if there were enough trees the amount and rate of absorption is highly uncertain and of course the carbon is only stored for the life of the trees. Third: aircraft are rapidly transforming carbon, which natural processes have locked into fossil fuels over millions of years, into carbon dioxide gas, in flights of seconds, minutes and hours - trees can't possibly absorb at a rate that can practically compensate for this.

David Camlin feels that sea levels are not going to rise because of melting ice sheets, saying 'As Archimedes could have told you if he had visited the Antarctic, ice shelves, which are afloat on the sea, do not cause any contribution to sea level rise when they melt.' ('Climate change debate', Bristol Evening Post letters, July 6). First: there are ice sheets on Antarctic land that are melting and this adds water to the sea (also the case for places like Greenland in the Arctic by the way). Second: when both floating ice and ice on land melts there is a highly significant change of colour from energy reflecting white ice to energy absorbing dark sea. This means less of the Sun's energy is reflecting back into space and more is absorbed, raising the temperature, expanding the ocean and causing sea level rise. Third: since 1945 the Antarctic Peninsula has experienced a warming of 2.5 degrees, approx five times the global average rise, in part because of the colour change on melting. The annual melt season there has increased by two to three weeks in just the past twenty years.

Its very important that we have well informed debate on climate change. People should use the work of the Intergovernmental Panel on Climate Change, set up by the United Nations, as their major source since they have looked at all the research on all sides of the debate and assessed its quality and consistency. They are saying that climate change is real, serious, urgent and our fault. To conclude differently is to fly in the face of the best expertise the world can currently assemble.